The susceptibility to collapse of loess soils from Normandy was examined in the triaxal apparatus both at natural moisture content (UU test), and after saturation (CU test). In order to prevent the sample from collapsing before the CU test, the lateral stress was applied before the samples were saturated.

Saturated loess soils show two very different types of behaviour depending on the void ratio. At high void ratios the stress path shows a collapsing structure which does not occur at low void ratios. The behaviour at natural unsaturated moisture content seems to depend on the clay content.

After a comparison with some results obtained on loess soils from the Paris area, the following conclusions are established:

  • that there is an analogy between the behaviour of collapsing loess soils and that of sensitive clays,

  • that the Feda criterion may be used to predict the collapse of a sample (Feda 1966), and

  • that there are difficulties in using this criterion for practical problems due to the in situ variation of void ratio.

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